For more than 40 years, private nonprofit volunteer-led free health clinics have been an "interim" solution to the deficiencies in our health system for the poor and underserved yet very little is known about them. In times of widespread concern about the safety net viability, this niche player has been overlooked, although free clinics serve the most disadvantaged populations. The limited literature suggests that free clinics are a response to a growing number of uninsured persons, and to an inadequate safety net, but this perspective may underestimate the range and complexity of factors that may influence free clinic founding and survival. It is important also to consider the potential role of population characteristics and environmental contexts. This dissertation project has five Specific Aims: 1. describe the distribution and attributes of free clinics in the U.S.; and determine if free clinics arise in reponse to... 2. health system gaps 3. "demand" by uninsured or poor persons; 4. the availability of potential "suppliers" of free care; and/or 5. environmental contexts. A theoretical framework guides the range of factors to be examined. The major hypotheses are: There will be more free clinics in metropolitan areas with...1. a greater number of persons who are dissatisfied with the quantity of available free care; 2. smaller public charity care capacity; 3. low levels of trust in physicians; 4. higher rates of uninsured and poor persons; 5. a greater density of churches; 6. a median population in "dominant status positions"; 7. a favorable legal environment for physicians providing free care; 8. a greater number of formal linkages with other institutions; and 9."moralistic" or "individualistic" philanthropic cultures, compared to "traditionalistic." A regression model suitable for count data will test these hypotheses. This study-the first of its kind-will establish a foundation of knowledge about free health clinics. Knowledge generated from this study will aid public policy decisions by describing the magnitude and nature of deficits in the existing safety net. It also will allow subsequent research to account for care delivered by free clinics.